Volt Ohm meter

Volt Ohm meter

IOPort51

NOT the voice of reason Jeep-CJ.com
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1977 cj-5
4.2 W/MC2100 carb, 4.0 head W/3 angle valves,SS Header,TFI ignition with MSB-6 offroad module,CS144 140 amp RPS alternator with remote regulator T-150,d-20,Dana 44 with OX lock and disk brakes. D-30 with Spartin locker,
skyjacker 2.5 lift?nitro shocks,31" BFG A/T off road.8000 lb Warn winch, original owner.=^)

2006 Toyota Tacoma
There are a lot of questions on this forum about electrical systems and the challenges they present. I have found that the one tool that is absolutely indispensable when working on a CJ is a VOM, volt ohm meter. I have the opinion that 99% of these problems will require a meter to solve.
For my own curiosity I am posting this pole. It's totally anonymous if you like.
I would like to know if you own a VOM, Know how to use a VOM and if you own a VOM and know how to use one.
When I say "know how to use one" I am referring to being able to being able to tell if there is voltage to a load, weather a relay or switch is open or closed and even how much current a load is drawing.
 
Good Question. I finally went and got a cheap analog VOM for troublshooting other things. I used to have a really nice digital one, long ago, but for $10, the one from Lowe's works just fine. we used to use them at the cable company for chasing shorts in the main line, or finding shorts in house wires. They are an indespensible item for troublshooting any electrical issue.
 
They don't have to be expensive, although I have a couple that were better than $200. I got a digital at Harbor freight a couple of weeks ago that will even do DC amps up to 20 amps, worked great to size the fuses and the wire for the new PDC I built. $20 and the only thing I don't like about it is it does not turn itself off.
 
The cable company bought us the expensive Fluke meters. They worked great, and were shock resistance (you don't always mean to drop things from the pole, but it happens). $20 sounds like a great deal, I could always use another tool.
 
Every garage should have one or two in case one has dead batteries witch you can check with the good one. :D
 
been there done that:D

Every garage should have one or two in case one has dead batteries witch you can check with the good one. :D
 
When I was installing wiring in 767s, I had a couple Fluke meters. Both of them got stolen with my toolbox a few years ago. Never had a good reason to pay over $50 or so for one since.
I had 2 at the start of this weekend, now I have 1. RIP to the oldest one I had, due to a failed circuit somewhere. I even checked it over with the other one! LOL
 
I've got a couple. When you need them there's almost no substitute. Though a length of wire and a spare tail lamp bulb will do in a pinch when you have nothing else.

Still, I like to have several since I can never seem to find the one I'm looking for.
 
A multimeter is indispensable. Sure there are times you can see if there is voltage by using a test light but if you have a bad alternator a test light wont' tell you the difference between 12 volts and 14 volts.
VOM meters are so cheap and easy to use everyone that works on cars should have one.
When I first used multimeters they were analog. The needle had different ranges and you had to know what number to read.
Product-2002513103153.jpg

 
A multimeter is indispensable. Sure there are times you can see if there is voltage by using a test light but if you have a bad alternator a test light wont' tell you the difference between 12 volts and 14 volts.
VOM meters are so cheap and easy to use everyone that works on cars should have one.
When I first used multimeters they were analog. The needle had different ranges and you had to know what number to read.
Product-2002513103153.jpg

my great great uncle was a radio tech in the navy in wwii. he gave me a meter similar to this one that he used in the war i still have it and it still works. i keep it put up and don't use it but i could. it doesn't have as many features though.
 
Purchased one a while back to use to test my battery and alternator. I then purchased a couple more at Harbor Freight in there bargin bin, as back ups, since they were inexpensive. I don't have much experience with them yet, but plan to learn/use them when I rewire. Anyone with newbie guides/tips for using them, please post a link for us who are just beginning. :D
Thanks
 
I did a google search and, as yet, have found no tutorials I would call great. keep looking.
 
Anyone with newbie guides/tips for using them, please post a link for us who are just beginning. :D
Thanks
digital multimeters are easy to use but you need to know when you would want to check voltage, when to check resistance (measured in ohms) and when to check current (measured in amps).
Voltage is the potential (power) to do work. A charged car battery sitting on the floor will have 12 volts across the posts. No current will be flowing since it is not connected up to a load. When I use my meter I am most often checking a voltage.

Lets say I have a light that isn't working. I might use my meter to see if it is getting voltage. With the light switch on and the bulb still hooked up I should read 12 volts. If I do read 12 volts I know it's getting the voltage it needs to work. Since the light isn't coming on I now suspect the bulb is bad. To double-check I can now check resistance through the bulb. To check resistance you should always remove the component, in this case the bulb. With the bulb in hand I try to read the resistance. Resistance is measured in ohms. My meter may say it has infinite ohms. Actually my meter may not do anything as I put the leads on a bulb that is bad. I would double check to make sure I really am holding the leads on the bulb correctly. To test my meter I would then touch both my leads together. Now the meter says 0 ohms. So the bulb is bad. Okay I have a bad bulb. No electricity can go through it.

Another measurement the multimeter can read is current. It is not very often that I read current. The reason is you must break the circuit to read current. Let's say I wanted to measure the amount of current going through that bulb I suspected was bad. I would have to remove one wire from the bulb. I would then put one lead on the wire that I removed. Put the other lead on the bulb where the wire was. Now with the lights on the current would have to go through my meter and then through the bulb. It is a pain to test a bulb this way.
It is even a bigger pain because the makers of multimeters have you plug the lead into a different spot on the meter. Notice the 3 places to plug leads into this meter.
mmeter12.jpg

Why do they do that? Because if you have your meter set up to read current and you accidentally try to read voltage then you will fry your meter. High current will flow through your meter. Actually the fuse in the meter will blow first. To read current they want you to take 2 steps - move the leads and turn the dial to current.

Now to put this all together with an analogy, Lets say you are at a large water tower. There is a big 12 inch pipe coming down from the water tower to ground level. There is a big cap on the pipe. The water behind that cap is under high pressure (think voltage). If you take the cap off you will be knocked across the street from the watter blast. Why? Because that big pipe has very low resistance (think ohms). You get the full power of that water pressure.
On the other hand if that was a straw coming down from the water tower there would be very little water coming out. Why? Because that little straw has high resistance. It may shoot very far from the pressure (same pressure as the big pipe). Actually that straw would probably burst. Even though it is small it would have to be a steel pipe to handle the pressure.
This tiny pipe with high pressure can be compared to an ignition wire. A spark plug needs very high voltage - thousands of volts. But it uses very little current (amps). An ignition wire has a very small conductor in the core but it has a very thick rubber insulation. Open the hood of a car with bad ignition wires at night and you will see sparks going from the wire to the engine block or any other ground. This is comparable to that old straw coming down from the water tower with lots of leaks.
There that's it. But now I wonder: Is any one still reading my ramblings?
 
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while busadaves explanation is good almost any meter bought new will have a small instruction booklet on how to take basic measurement and do basic tests with the meter. even the little el cheapo ones from harbor freight has them. i got one of the little cheap ones for free from hf and it came with one. little note to anyone who is interested hf will honor online coupons in store thats how i got the little red meter they have for free. at the time it was only like $5-$6 but hey i got it free.
 
Just a little plug for the cheap meters. Most are analog (needle moves across the scale), and actually put a very small load on the circuit being tested. Digital meters are much more sensitive, and this can sometimes, but not often, give false readings. I have seen digital meters show voltage through the carbon track in a blown fuse.
Main thing to remember when using a VOM is volts is volts and ohms is ohms. Volts on the ohm setting will smoke the internal fuse.
 

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